This invention relates to a four-cycle internal combustion engine and more particularly to an improved crankcase therefor.
In many forms of four-cycle internal combustion engines, the crankcase, in addition to providing a surrounding location for the crankshaft, also contains the lubricant, which is circulated through the engine for its lubrication. This lubricant is then returned to the crankcase for recycling. Such lubrication systems are called "wet sump engines."
There is a disadvantage with this type of lubrication system. Because the crankcase chamber must contain all of the lubricant for the engine, there tends to become an increase in height of the overall engine. The reason for this is that it is desirable, if not essential, that the crankshaft and other rotating components in the crankcase do not contact the oil. If they do, they will cause churning and aeration of the oil. This also creates drag on the rotating components.
Therefore, it has been the practice to provide oil pans that have a length which is substantially equal to the length of the engine. However, this presents some problems in and of itself. If the engine is mounted in a fore and aft direction so that the crankshaft rotates about an axis longitudinal of an associated vehicle, then sudden accelerations or decelerations can cause the oil level in the crankcase to change. Since the oil is picked up through a pick-up device at a specific location in the crankcase which is generally at its midpoint, this means that the oil may actually move away from the pick-up. Thus, air rather than oil will be pumped, obviously not a desirable condition.
A similar problem exists if the engine is placed transversely in the engine compartment, as it is in many front-engine, front-wheel drive or rear-engine, rear-wheel drive applications. With such an arrangement, sudden changes in direction such as cornering to the right or the left can cause a similar problem to occur with the oil pick-up.
It is, therefore, a principal object of this invention to provide an improved crankcase assembly for an internal combustion engine.
It is a further object of the invention to provide an improved crankcase assembly for an internal combustion engine that will accommodate sufficient oil and yet not be obtrusive in size and also reduce the likelihood of sloshing of the oil in the crankcase resulting in the pick up of air rather than oil.
In order to provide large volumes, the exterior surface area of the crankcase also becomes quite largely since it is desirable to maintain light weight, the crankcase is generally formed from a thin material, and this can give rise to the generation of noises. That is, the extensive but thin-walled crankcase may resonate and create objectionable sounds.
It is, therefore, a still further object of this invention to provide an improved crankcase construction for an internal combustion engine wherein the crankcase is configured to provide adequate volume, and yet its surface area is such that sounds cannot easily emanate from the crankcase due to vibrations.